An innovative system of concrete decking will keep busy Eglinton Ave. open, if a little slower, as construction continues underground.

Metrolinx will have to dig up the road to build the stations on Eglinton but when it does a concrete decking system similar to the one pictured here will be used. It was used to create a road base during construction of the Red Line subway in Los Angeles. The panels can be pulled up to remove dirt during excavation or later, to pour concrete.

When it comes to easing gridlock by building a new transit line, nobody in charge of the Crosstown LRT denies traffic will get worse on Eglinton Ave. before it gets better.

But Metrolinx officials insist that motorists will be able to drive on the street while the LRT is being built. Even at the height of construction, at least one lane of traffic will continue to move in each direction.

Drivers and residents in nearby neighbourhoods should, however, prepare for turn restrictions, some side-street closures and the disappearance of curb lane parking in the years before the Crosstown’s scheduled 2021
opening
.

Although much of the tunnelling will be invisible to people on the streets, the giant boring machines will cause disruptions where they are being dropped into the earth and lifted out.

At Allen Rd., for example, the machines will surface to the west of Eglinton West Station and be dropped back down on the east side to avoid interfering with the subway.

The
impact
— narrowing of lanes, dust, noise and congestion — will be felt around Black Creek Dr., the site of the tunnelling machine launch shaft and will creep eastward as crews begin the utility work in preparation for the tunnel and station construction. But the most significant disruptions will come in 2015, when station building begins in earnest.

That’s when crews dig down, rather than tunnelling sideways through the earth.

In the past, wooden decking was used to cover road construction. It was like driving on a washboard, says Metrolinx executive vice-president Jack Collins.

But for the tunnelled portion of Eglinton between about Black Creek and Brentcliffe Rd., crews will use a system that Collins says he first saw in Los Angeles.

During the 1990s, L.A. was extending the Hollywood section of its Red Linesubway and the Pasadena-downtown Gold Line LRT.

Related

Instead of detouring traffic around construction, transportation engineers came up with a system of laying precast concrete decking across a lattice of steel supports. It allowed construction to continue below the street, and cars could use the decking as a temporary road surface.

The new transit stations on Eglinton are essentially being built as concrete boxes. The east and west concrete “headwalls” of the stations get built in advance of the arrival of the tunnelling machines. The giant boring equipment then punches right through the concrete, creating a perfect seal at each end.

The north and south walls of the box typically span the width of the street, curb to curb. The contractor Metrolinx hires to build the stations will create a concrete wall along one side of the street, parallel to the sidewalk, running 20 to 30 metres below the street.

While that’s being built, traffic will be shifted to one side of the road as the heavy construction machinery works along the opposite curb. Once the first wall is built, the machinery will move to the other curb and traffic will travel down the opposite side of the street.

Signs will be posted locally and in key spots, such as along Highway 401, warning of slowdowns. To let residents and businesses know what to expect, Metrolinx will also use the Crosstown website and distribute flyers through its community offices and meetings.

Once the station walls are built, the contractor constructs a pier down the middle of the station box. At that point, the traffic is pushed toward the curbs on either side of the road. That pier helps support the steel beams that form the lattice.

Crews dig down far enough that the heavy equipment can be lowered into the pit by a construction crane and the deck panels are then dropped on top of the beams, like a drop ceiling.

In many cases, gas lines, wires and utilities are hung from the steel deck beams so they don’t have to be relocated. Workers climb stairs in and out of the pit.

“Think of this as a big concrete boat,” says Collins. “At the end it gets filled in and they restore the road.”

Traffic volumes on Eglinton

Traffic levels vary on the Crosstown route.

West of Laird, the route is used by 20,000 to 30,000 cars a day, with the heaviest volumes closest to Allen Rd.

East of Laird, volumes exceed 40,000 cars per day.

Near the Don Valley Parkway, about 60,000 cars a day travel along Eglinton.

Buses travelling along Eglinton W. from Yonge St.: There are 1,257 east- and westbound buses on an average weekday. The majority, 791, run between Eglinton and Renforth Dr. Saturdays are almost as busy with 1,014 Eglinton buses. Another 1,304 buses run east of Yonge St. along Eglinton on weekdays; 970 on Saturdays.

Source: City of Toronto and the TTC

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